Physical examination, a discussion of symptoms, and medical tests are the best ways to determine if a person has Addison's disease.
The goal of the medical test is to first determine whether the levels of cortisol (in the blood) are sufficient, and then to identify the cause (primary or secondary) with the adrenocorticorticotropic hormone (ACTH) test and the corticotrophin-releasing hormone (CRH) stimulation test.
The ACTH stimulation test looks at the adrenal glands' ability to produce cortisol. Blood and urine cortisol samples are collected before and after an injection of synthetic (manmade) ACTH. Low or no cortisol in samples after the injection indicates Addison's disease or primary adrenal insufficiency.
When the response to the ACTH test is abnormal, a CRH stimulation test is helpful in determining the cause of adrenal insufficiency. CRH is produced by the hypothalamus in the brain to stimulate the pituitary gland to produce the ACTH, which then stimulates the adrenal gland to produce cortisol and aldosterone. A synthetic CRH is injected, and the blood cortisol is measured before and after the injection. Individuals with Addison's disease respond to the CRH test by producing high levels of ACTH but little cortisol. On the other hand, if CRH fails to stimulate the pituitary gland to produce ACTH, secondary adrenal insufficiency is suspected.
Other tests, such as imaging technologies (e.g., CT scan or MRI), are used to examine the size and shape of the adrenal glands, the pituitary gland, and the hypothalamus.